The invention relates to a method and apparatus for attaching, and detaching, a centrifugal pump to a tank containing a liquid or suspension, without the necessity of emptying the tank. There are numerous applications in industry wherein a pump is mounted directly to a tank to effect pumping of liquid from the tank. One particular application is the mounting of the centrifugal pump to a bottom portion of a tank containing a cellulosic fiber suspension, preferably of relatively high consistency (i.e. about 8-15%). Typically such pumps are mounted to such tanks--as disclosed in copending application Ser. No. 139,162 filed Apr. 7, 1980; and Canadian Patent No. 1,128,368, the disclosures of each of which are hereby incorporated by reference herein--so that a portion of the pump rotor extends into the interior of the tank through an opening in the bottom of the tank. When it is desired to detach the pump from the tank in such systems it is necessary to drain the tank before detachment. This is an exceptionally tedious, cumbersome, and wasteful practice which it is highly desirable to avoid. According to the method and apparatus of the present invention it is possible to avoid draining of the tank before detachment of the pump, and the pump can be readily detached, repaired or replaced, and reattached.
The basic apparatus features of the present invention are: Means defining a passageway in the bottom of the pump housing, the passageway having a diameter greater than the maximum diameter of the pump rotor (e.g. the impeller blades), and a rotor support member mounting the rotor and axially movable within the passageway. An O-ring, or like sealing means, provide sealing engagement between the pump housing and rotor support member during axial relative movement therebetween. The length of travel of the axial movement is sufficient to move the rotor from its original, first, position wherein a portion thereof extends into the interior of the tank, to a second position wherein no portion of the rotor is within the interior of the tank. A closing means is provided for closing the tank opening after movement of the rotor to its second position, the closing means preferably comprising a closing member mounted for pivotal movement within the interior of the tank, and controlled by an actuator exterior of the tank. The closing member is movable from a first position in which the closing member is arcuately spaced from the opening, to a second position in which the closing member engages a sealing member surrounding the opening, and substantially prevents passage of liquid or suspension from the tank interior through the opening.
When practicing the method of attachment and detachment of a pump to a tank, according to the invention, the rotor is axially moved to its second position, the closing member is moved so that it closes off the opening, and then preferably the interior of the pump housing is flushed with a fluid (e.g. water) to remove fiber suspension, or other materials, therefrom. Then the entire pump housing is detached from the tank. When the pump is to be reattached to the tank, first the pump housing is reattached to the tank with the rotor in its second position, then fluid is supplied to the interior of the pump housing to substantially equalize the pressure on opposite sides of the closing member; then the closing member is pivoted to its arcuate position wherein it does not block the tank opening; and then the rotor is moved axially so that a portion thereof passes through the tank opening into the interior of the tank.
It is the primary object of the present invention to provide a simple and effective method and apparatus for the attachment or detachment of a centrifugal pump to a tank containing a suspension or liquid. This and other objects of the invention will become clear from an inspection of the detailed description of the invention, and from the appended claims.